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		<H2><A NAME="HDREXVP" ></A>5.4 Executing a Visual Program</H2>
		<A NAME="IDX647"></A><A NAME="IDX648"></A>
<P>
After you set up a visual program in the VPE window and build any desired
Control Panels (or after you open an existing visual program file), you can
execute the visual program program.
The resulting image appears in the Image window.
This section explains how to execute a visual program.
Section <A HREF="usrgu040.htm#HDRUSEIMAG">6.1 , "Using the Image Window"</A>
describes how to manipulate images in the
Image window by using direct interactors.
You can also manipulate images in the Image window using interactors in
the Control
Panels, the Colormap Editor, and the Sequencer.
(For more information on these tools, see <A HREF="usrgu043.htm#HDRBUICO">7.1 ,
"Using Control Panels and Interactors"</A>,
<A HREF="refgu035.htm#HDRCOLRMAP">Colormap</A>, and <A
HREF="refgu134.htm#HDRSEQUENC">Sequencer</A> in <I>IBM Visualization Data
Explorer User&#39;s Reference</I>.)
<P>
You can execute the visual program from the <TT><STRONG>Execute</STRONG></TT>
menu of
a VPE window, a Control Panel, an Image window, or
a Message window.
The options are the same in all four windows.
When a visual program is executed, an Image window is created if one is not
already open.
(You can also control execution using the Execute module.
See <I>IBM Visualization Data Explorer User&#39;s Reference</I>.)
<TABLE><TR><TD ALIGN="LEFT" VALIGN="TOP"><B>Note:</B></TD><TD ALIGN="LEFT"
VALIGN="TOP">If the <TT><STRONG>Execute</STRONG></TT> options are grayed-out,
your
workstation may not be connected to the server.
For information about connecting to the server, see
<A HREF="usrgu049.htm#HDRCONSERV">9.3 , "Connecting to the Server"</A>.
</td></tr></table>
Although you can initiate execution from the Control Panel, VPE,
Image, and Message windows, you may find it more efficient to
execute your visual program through the Control Panel menu (if you
are using a Control Panel).
This efficiency is due to the ease with which you can change inputs
with interactors and initiate execution.
<P>
You can choose one of four options from the <TT><STRONG>Execute</STRONG></TT>
menu when executing a visual program.
Select the first option, <TT><STRONG>Execute Once</STRONG></TT>, to execute
the program once, using the values currently set in
the interactors.
If you change any interactor values after execution, the visual program does not
automatically execute; you must again choose an option from the
<TT><STRONG>Execute</STRONG></TT> menu to execute the altered program.
<P>
Choosing the <TT><STRONG>Execute on Change</STRONG></TT> option causes
the visual program to execute every time you change an
interactor setting.
If you change values faster than Data Explorer can generate images, the system
executes the program as quickly as possible, always using the
current settings at the time an execution cycle begins.
If you modify your visual program while <TT><STRONG>Execute on
Change</STRONG></TT>
is enabled, then the option automatically becomes disabled.
After the changes are made, you can reenable it.
<P>
Choosing <TT><STRONG>End Execution</STRONG></TT> while the visual program is
executing
causes execution to stop after the currently executing module.
<P>
The final <TT><STRONG>Execute</STRONG></TT> menu option is
<TT><STRONG>Sequencer</STRONG></TT>.
If you select this option, and a Sequencer tool is present in the visual
program, the Sequencer appears (see <A HREF="#HDRSEQUEN">"Using the
Sequencer"</A>
for more information).
While the Sequencer runs, you can change interactor settings, and those
changes are reflected in subsequent frames generated by
the Sequencer.
The <TT><STRONG>Execute Once</STRONG></TT> and <TT><STRONG>Execute on
Change</STRONG></TT> options are grayed out when the Sequencer
is running, but when you pause the Sequencer, you can
use those two options to explore the particular
frame the Sequencer paused on.
<P>
While the visual program is executing, the <TT><STRONG>Execute</STRONG></TT>
option on
the menu bar is highlighted.
It remains highlighted until execution is finished.
If <TT><STRONG>Execute on Change</STRONG></TT> is selected, the
<TT><STRONG>Execute</STRONG></TT> option on the menu bar is
highlighted with one color during execution, and
another color outside of execution cycles.
<P>
<H3><A NAME="HDRSEQUEN"></A>Using the Sequencer</H3>
<A NAME="IDX649"></A>
<A NAME="IDX650"></A>
<A NAME="IDX651"></A>
<A NAME="IDX652"></A>
<P>
The Sequencer allows you to "animate" a visual image and is very
easy to use.
The process is rather like running a video cassette tape:
You can play it forward or backward, stop it, pause, and so on.

The Sequencer Control panel consists of 8 buttons as shown in
<A HREF="#FIGVCRCON">Figure 33</A>.
<P><B><A NAME="FIGVCRCON" HREF="../usrguide.htm#FT_FIGVCRCON">Figure 33. Sequence
Control Panel</A></B>. The first two buttons at top left are Loop and
Palindrome. The others are: Step (&lt;<TT><STRONG>||</STRONG></TT>&gt;), Counter
(<TT><STRONG>...</STRONG></TT>), Back (&lt;), Forward (&gt;), Stop (&sqbul;),
and Pause (<TT><STRONG>||</STRONG></TT>).<BR>
<B><BR><CENTER><IMG SRC="../images/seqctrl.gif" ALT="Figure seqctrl not
displayed."></CENTER><BR></B><BR>
<P>
The &gt; button starts the animation sequence and plays forward. The
&lt; button plays the sequence in the opposite direction.
<P>
The &sqbul; button stops the animation and resets the animation to the
beginning of the sequence, while the <TT><STRONG>||</STRONG></TT> button
pauses the animation at the current frame.
<P>
The <TT><STRONG>Loop</STRONG></TT> button causes the animation to loop; that is
to go from beginning to end, reset to beginning, play to end, and so on
until terminated by either pause or stop.
<P>
The <TT><STRONG>Palindrome</STRONG></TT> button causes the sequence to be
played from beginning to end, and then from end to beginning.
<P>
<TT><STRONG>Loop</STRONG></TT> and <TT><STRONG>Palindrome</STRONG></TT> can be
pressed simultaneously, resulting in an continuous forward and reverse
animation.
<P>
The &lt;<TT><STRONG>||</STRONG></TT>&gt; button causes the behavior of
the &gt; and &lt; buttons to become single-step mode. Each time
one of these buttons is pressed, the animation advances one frame in the
specified direction.

<P>
The <TT><STRONG>...</STRONG></TT> button opens the Frame Control dialog.
The Frame Control dialog box (see <A HREF="#FIGVCRFR">Figure 34</A>) is used to
specify the first, "next," and last (end) frames, the number
of frames, and the increment between successive frames.
<P>
If a frame is being displayed, the current frame number appears in the
Frame Control dialog box, next to the word "Current," and a
corresponding colored marker is shown on the slide bar.
A colored marker indicating the position of the next frame is also
shown.
Black markers indicate the positions of <I>start</I> and
<I>end</I> relative to the next range of min to max.
<A NAME="IDX653"></A>
<P><B><A NAME="FIGVCRFR" HREF="../usrguide.htm#FT_FIGVCRFR">Figure 34. Sequencer
Frame Control Dialog Box</A></B><BR>
<B><BR><CENTER><IMG SRC="../images/framctrl.gif" ALT="Figure framctrl not
displayed."></CENTER><BR></B><BR>
Values for the Start, Next, and End frames are set by&#58;
<UL COMPACT>
<LI>Entering a value in the text field of the stepper
buttons
<LI>Using the stepper controls
<LI>Moving the position marker.
</UL>
<TABLE CELLPADDING="3">
<TR VALIGN="TOP"><TD><P><B><TT><STRONG>Start</STRONG></TT>
</B></TD><TD><P>The starting value for the sequence.
By default, set to the value in the Min field, in a
new program.
To change the Start field, use the stepper controls or select the field
and enter the new value or use the Start marker.
If you change the value in the Min field, then the Start field is set
to that new value.
If you are working with a saved program, then the Min and Start fields
are set to the values that were saved.
</TD></TR><TR VALIGN="TOP"><TD><P><B><TT><STRONG>End</STRONG></TT>
</B></TD><TD><P>The ending value for the sequence.
By default, set to the value in the Max field, in a new program.
To change the End field, use the stepper controls or select the
field and enter the new value or use the End marker.
If you change the value in the Max field, then the End field is set to
that new value.
If you are working with a saved program, then the Max and End fields
are set to the values that were saved.
</TD></TR><TR VALIGN="TOP"><TD><P><B><TT><STRONG>Current</STRONG></TT>
</B></TD><TD><P>Displays the current frame number.
</TD></TR><TR VALIGN="TOP"><TD><P><B><TT><STRONG>Increment</STRONG></TT>
</B></TD><TD><P>By default, set to 1.
To change the increment, use the stepper controls or select the field
and enter the new value.
</TD></TR><TR VALIGN="TOP"><TD><P><B><TT><STRONG>Next</STRONG></TT>
</B></TD><TD><P>By default, set to the value in the Start field, in a new
program.
You can set the Next field to any value between the Start and End
values: the Sequencer will begin running at that value.
(When the Sequencer is in loop mode, subsequent loops begin at the value in
the Start field.)
</TD></TR><TR VALIGN="TOP"><TD><P><B><TT><STRONG>Min</STRONG></TT>
&nbsp;and&nbsp; <TT><STRONG>Max</STRONG></TT>
</B></TD><TD><P>Specify the allowed range of sequence values.
These are text fields that can be altered.
Data Explorer ensures that the value in the Start field is greater than or equal
to the Min value, and the value in the End field is less than or
equal to the Max value.
</TD></TR></TABLE>
<TABLE><TR><TD ALIGN="LEFT" VALIGN="TOP"><B>Note:</B></TD><TD ALIGN="LEFT"
VALIGN="TOP">If the images change more quickly than you would like, use the
<TT><STRONG>Throttle...</STRONG></TT> option (see
<A HREF="usrgu040.htm#HDRSPEED">"Changing the Rate of Frame Display:
Throttle..."</A>).
</td></tr></table>
<P>
<H3><A NAME="Header_124" ></A>Using a Data-Driven Sequencer</H3>
<P>
The Sequencer can be <I>data driven</I>, meaning that its minimum,
maximum, and step values can be set by connecting the output of
a tool to the input of a Sequencer in the VPE or by a
value typed into the Sequencer&#39;s Configuration
dialog box, rather than by using the
<TT><STRONG>Frame Control</STRONG></TT>
panel.
<P>
If the Sequencer is data driven, then the information transmitted by
connection or set in the Configuration dialog box overrides
values set in the <TT><STRONG>Frame Control</STRONG></TT>
panel.
<P>
A data-driven Sequencer allows you to create visual programs that will
work with a variety of input data sets without your having to reset
Sequencer attributes.
For example, if the Sequencer minimum is set to zero and its maximum to
the number of steps in a series, it can be used to drive the Select
module to select each member of the series in turn.
<P>
The inputs are summarized in the corresponding module description
in <I>IBM Visualization Data Explorer User&#39;s Reference</I>.
<P>
Each time an input to a data-driven Sequencer is changed (for example,
by importing a new data set) the Sequencer is reexecuted, updating
its attributes.
<P>
<H3><A NAME="HDRERMSGS" ></A>Error Messages</H3>
<A NAME="IDX654"></A>
<P>
If Data Explorer encounters an error in your visual program while executing it,
an error
message is displayed in the Message window (see <A
HREF="usrgu046.htm#HDRDEBUG">8.2 , "Using the Message Window"</A>).
The name of the tool in which the error occurred is shown in the
window.
Pull-down menu options enable you to quickly locate
the tool that caused the error.

		<P>
The title of the tool icon in the visual program that caused the error is
displayed in a different color in the VPE until you execute
the program again.
When the error occurs, execution stops only in the path where the error
is; other paths continue.

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